Process of producing synthetic hydrocarbon



Feb. 27, 1940. J. E. HARVEY, JR 2,191,466

PROCESS 0F PRODUCING SYNTHETIC HYDROCAHBON F11-ed sept. 22, 195'/ @LMU 45 From separator I Patented Feb'. 27, 1940 UNITED STATES PATENT OFFICE PROCESS F PRODUCING SYNTHETIC HYDROCARBON Application September 22, 1937, Serial No. 165,183

Claims. (Cl. 1964-62) The invention relates to the production of wood preservatives and of products incidental to said process. I

It is an object of the invention to improve upon 5 the process described and claimed in PatentNo. 2,082,885 granted to me on June 8, 1937.

It is a further object of the invention to provide an improved process oi the nature referred to which includes the removal of materials, such as vfree carbon and/or material insoluble in benzol which cannot be, or can only with difculty be hydrogenated, whereby to increase the yield of creosote or to facilitate working.

A further object of the invention is to control the saturation of the end product whereby to improve the color of the end product and/ormake the color more stable.

The process described by my former 'Patent No. 2,082,885 changes pitch to creosote, from 80% to 100%. As a result of the process of the pres- .ent invention, pitches which were heretofore changed in the order of 80% may now be readily changed a higher percentage into creosote, and it is an object of the invention to more nearly approach 100% conversion.

, It is a further object to improve the process of producing an"8020 wood preservative.

It is a further object of the invention to convert a large .percentage of pitch into a wood preservative and substantially the whole of the remainder thereof into a lighter and more valuable product.

Further objects of the invention will appear from the following description when read in conf nection with the accompanying drawing in which the figure illustrates a flow sheet which may be utilized to carry out the various aspects of the process.

As shown in said figure, numeral 4 represents 40 a reaction cham-ber from which the beneciated material may be conducted through conduit 5 to high pressure gasseparator 6, the gas removed therefrom being drawn oil through conduit 1 controlled by valve 8.

li the material may be conducted through conduit 8 to low pressure gas separatorv 9 from which the gas may be conducted through conduit I0 under control of valve II. The gas from these separators may be wasted or 50 may be-returned to the reaction chamber.

From separator 9,the material may be conducted through conduit I2 either to still I3 or to still I4 as controlled by valves I5 and I6, and the residue from still I3 may be conducted to still I4 l or to discard as controlled by valves I1, I8.

The volatiles from still I 3 when separated to produce the wanted material as creosote may be conducted to storage through conduit I9 or when the volatiles are to'be further cycled in the process may' be conducted to still I4 as controlled by 5 valves 20, 2l. When pitch is the starting material, still I3 .may be cut out of the system and new pitch may be introduced to still I4 through conduit 22. When tar is the material being op: erated upon the still- I4 is utilized as a pre-heater 10 and to strip the material of already existing creosote to pass through storage to conduit I9 controlled by valve 23.

` In the event that the material under treatment is pitch, the still I4 becomes a preheating means for the pitch and a mixer of this pitch with the volatiles from still I3 when'the steps described herein as interspersed between the creosote distillation steps are carried out.

- The residue from still I3 during the cyclic dis- 20 tillation steps is conducted to still I4 for mixture with fresh material to be recycled through the conduit 24 to the reaction chamber. A high pressure pump for material to be treated is indicated at 25, and a high pressure pump for hydro- 25 gen supply is indicated at 26.

To the end of approaching more nearly volume for volume conversion of such pitches as cannot be or only with difliculty can be so converted by the process of my Patent No. 2,082,885, the present invention provides the added step of removing free carbon and/or benzol insoluble material from the feed stock either prior to the rst hydrogenation step or at an intermediate step of the process.

If such removal is not practiced it is possible that after an indeterminate number of cycles in a continuous process, the percentage of material which cannot be hydrogenated may build up to an amount to interfere with operation as by clogging 40 A lines or valves, ror reducing the percentage of synthesis -per cycle below that which is commercial. Any such removal should at least be operative to limit the build-up of the objectionable materials to a percentage where the process is 45 commercially protable.

The removal of objectionables may be carried out by a ltering or centrifuging of the fresh feed. This necessitates the treatment oi' an inordinate quantity of material and it is therefore preferred to apply the removal step to the residue of a distillation step as the said residue is recycled to hydrogenation.

A desirable form of removal is the employment of two stills in the flow sheet and the division of the hydrogenated material between them. One

still will receive a great majority of the oW--say,-

from 90% to 99% of the hydrogenated material and the residue from this still will be recycled to the hydrogenation chamber. 'I'he remaining still will receive only from, say, 1% to 10%' of the hydrogenated material, the amount depending on the nature of the pitch or tar under treatment. 'I'he percentages named are for purpose of illustration only.

The small still will be operated to remove all advisable volatile matter which vis recovered ln the distillate and may be added to the feed to the hydrogenation chamber, or mixed directly with the natural or synthetic creosote. The residue from the small still may be discarded insofar as the production of synthetic creosote is concerned and utilized otherwise in the arts.

The thus discarded residue obviously contains a considerable material other than free carbon .or benzol insolubleand has been at least once through the hydrogenation cycle. Apparently the hydrogenation has an effect not only to synthetize creosote but to so affect the portion of the material recovered as residue, boiling above creosote, as to produce a paving or roofing material having vadvantages over the usual pitch remaining after removal of creosote from coal tar, or from the material resulting as volatiles from the direct recovery still.

The nature of this improvement appears to be less variation of penetration with atmospheric temperature changes, and a longer-life due to the fact that a lower penetration material may be adopted for summer use.

'Ihe percentage of now to the smaller still, above referred to will desirably be the observed percentage increment of objectionable material per cycle of treatment. y

An alternate method of removal of objectionables is the carrying on of `cyclic synthesis to thel point where the build-up of 'objectionables unduly hampers the synthesis and thenla use in the still of atemperature which will drive off all advisable volatiles, and the discarding in toto of the resulting residue insofar as the creosote industry is concerned.

Instead of raising the temperature of the still as above described, the volatiles may be swept out by streaming any hydrocarbon gas or the like through the still which step will have the. same effect as raising the temperature of the still.

In either case the volatiles removed are returned to the hydrogenationv cycle, if-desired, used as such, or blended with any of the creosotes.

A valuable feature of the invention resides in the production of a distillate representing-substantially 80% or more of the coal tar or the like and wherein substantially all the free carbon or insoluble in benzol is left in the residue.

As a means of accomplishing this, The Barrett Direct Recovery still may be operated at a high temperature, set to recover all advisable volatile matter from coal tar. The vapors are fractionated to separate the permissible creosote, the higher boiling point vapors going to a separate channel. The resultant pitch from the direct recovery still is sent to an appropriate coking thetic creosote is combined with the natural creosote the resultant wood preservative will be substantially volume for volume as compared with the original coal tar and the blended creosote will have higher toxic value than the natural creosote of comparable boiling range.

A further valuable feature of the invention is the production of a wood preservative from starting materials falling in the group comprising coal tar or residues therefrom, and residues of the naval stores industry such as rosin, rosin oil pitch, pine tar and pine tar pitch wherein the material is treated in principle according'to the process of my Patent No. 2,082,885 to substantially total saturation producing a wood preservative which is substantially color stable, that is, the wood preservative so recovered as a distillate will not substantially go olf color.

It is found that the saturated distillation product referred to is particularly valuable as a otation agent in the copper, lead, zinc and kindred recovery industries by the flotation method. I am at present unable to explain the unexpectedly good results owing from use of my synthetic creosote as a flotation reagent.

It has been proposed to produce an 80-20 oil from coal tar by one hydrogenation step properly controlled and without distillation. In accordance with the present invention the production of an 80-20 oil is expedited by rst stripping the coal tar of natural creosote as to 355 C., then hydrogenating the resulting pitch for l pheres hydrogen pressure: The conditions should be so chosen as to not produce any substantial quantity. of low boiling fractions which must bediscarded. The thus treated mass is then freed of gas and mixed with the natural creosote to provide the wanted 80-20 oil of a high grade.

In accordance with the process of my Patent No. 2,082,885 the whole of the residue of each cycle is treated alike as to hydrogenation. A feature of the present invention providing an improvement of the former process is a process wherein the hydrogenated pitch is distilled to an' upper limit of say 380 C. and the vapors are fractionally condensed. The vapors condensing between 355 and 380 C. going to one channel and from 210 to 355 C. to another channel rep- 'resenting the desired end product. The residue from the dstillation is then hydrogenated separately using the preferred catalyst for pitch of that grade after which the thus partially beneiiciated mass may be blended with the 355 to 380 C. cut, with subsequent completion of lthe extant cycle of hydrogenation using a different catalyst if desired, and if any to prepare for the next distillation step. Optimum catalytic conditions may thus be had when catalysts are used and the percentage of synthesis per cycle may be increased.

'A further feature ofthe invention combines the production of Wood preservative and lighter and more valuable products, as for instance, benzine or the like. In carrying out this feature of the invention the starting material as tar or pitch is hydrogenated under conditions to produce a predetermined percentage of low front ends, as say, 20% below 210 C. The conditions to produce this result with an average coal tar are found to be a temperature of 200 C. a hydrogen pressure of from 100 to 300 atmospheres and the time is determined by withdrawing and testing samples.

The thus hydrogenated material is then fractionated and separated into distillates of several ranges. Assuming that benzine and creosote'are wanted, the separation would be into cuts having to 80 C., 80 to 210 C., and 210 to 355 C. boiling ranges. The first and last named being wanted materials are passed to storage. The 80 to 210 C. cut may be combined with the residue above 355 C. and recycled to hydrogenation, thus forming a basis for a portion of the next 0 to 80 C. cut when hydrogenated.

As a preparation for any of the above process steps, to the end of getting rid of objectionables as free carbon or benzol insolubles, it is a feature of the invention to subject the starting material for hydrogenation, to vacuum distillation. By so doing, substantially all the material capable of being hydrogenated is recovered in the distillate without degradation due to cracking. The objectionables are substantially all left in the residue. f A

As examples of the material which may be produced by the process with toxic properties in excess of those extant, trade and manufacturing speciiications currently in force prescribe the following boiling limits for coal tar wood preservatives: (a) Neville low boiling creosote all distilling between 140 C. and 350 C.; (b) American Wood Preservers Association, Dewey S 47, Class "d, not more than 5% distilling at 210 C.; (c)

Prussian State Railways (Hydrocarbon Oils & Saponiable Fats 8: Waxes, D. Holde, translated by Edward Mueller, 2d English edition, John Wiley & Sons, Inc., New York, 1922, page 338), not more than 3% distilling at 150 C.

I claim:

1. The method of producing a preservative wood impregnant more toxic than the starting material which comprises: subjecting a pitch obtained from a material in the group consisting of coal tar and rosin pitch to toxicity-inducing hydrogenation with the time, temperature and pressure so controlled that when the hydrogenated product is distilled up to a temperature to recover the desired product as a distillate said distillate will have no greater percentage of ends boiling below 210 C. than is permitted in specications accepted in the trade for wood preservative creosote directly recovered by distillation of coal tar and so controlled that the percentage of materials in a distillate boiling between 210 C. and 355-C. required by said specications is prolduced; distilling said hydrogenation product until the distillate has no greater percentage oi ends boiling above 355 C. than is permitted by said specications to secure a wood preservative with induced toxic properties; repeating the cycle; and at intervals during such repetition when accumulation of material not susceptible of hydrogenation under the conditions of the process interferes with operation, interspersing a step of removing substantially all volatiles from the residue of a distillation step for recycling, and discarding the residue from such interspersed step.

2. Tire process of producing hydrogenation products having induced toxic properties from tar or pitch derived from wood or coal and containing fractions not responsive to hydrogenation which comprises: carrying out recurring cycles of hydrogenation so limited as to produce not more than 20% of fractions boiling below 210 C. alternating with fractional distillation to secure wanted materials boilingr below 210 C. and between 210. C. and substantially 355 C.; repeating the hydrogenating steps on the residue of such distillation steps interspersing in said cyclic distillation steps at intervals when build-up of fractions not susceptible of hydrogenation under conditions of the process interferes with operation another distillation step at a temperature to remove substantially all volatiles from the hydrogenated material; discarding the residue of the latter from the process carrying the objectionables with it; condensing said volatiles; adding fresh starting material to the condensed volatiles; and continuing the cyclic steps as before.

3. The method of producing a wood preservative impregnant more toxic than the starting material, which comprises: subjecting a material derived from distillation of a material chosen from a group consisting of relatively high boiling distillation products of coal and wood, containing fractions not responsive to hydrogenation under the conditions of the process, to recurring cycles of toxicity-inducing hydrogenation each so limited as to produce no greater percentage of fractions boiling below 210 C. than is accepted by specications in the trade for a wood preservative, alternated with steps of distillation of the hydrogenated material limited to remove the highest boiling point fractions provided by said specifications in the product; interspersing in said cycles of hydrogenation and distillation steps at intervals, distillation steps at a temperature to remove substantially all volatiles from the vkfurther cyclic hydrogenation and distillation whereby to induce toxic properties.

4. The method of producing a wood preservative impregnant more toxic than the starting material, which comprises: subjecting a relatively high boiling material derived from distillation of a material chosen from a group consisting of coal and wood, containing fractions not responsive to hydrogenation under the conditions of the process, to recurring cycles of toxicity-inducing hydrogenation each so limited as to produce no greater percentage of fractions boiling below 210 C. than is accepted by specications in the trade for a wood preservative, alternated with steps of distillation of the hydrogenated material limited to remove the highest boiling point fractions provided by said specifications in the product; interspersing in said cycles of -hydrogenation and distillation steps at intervals, distillation steps at a temperature to remove substantially all volatiles from the residue of a preceding cyclic distillation step assisted by streaming a gas through the residue; discarding the residue from each interspersed distillation step and subjecting said volatiles to further cyclic hydrogenation and distillation whereby to induce toxic properties.

5. The process of claim 3 including the step of adding fresh starting material at recurrent cycles and after interspersed distillation steps to preserve the volume of material under treatment.

JACQUEIJN E. HARVEY, Jn. 

